This invention relates to an apparatus and a method for direct chromatographic analysis of filter trapped analytes. Particularly the invention relates to an apparatus and method for receiving and injecting trapped volatiles directly from a solid filter medium into a gas chromatograph for analysis.
The field of chromatographic analysis has been generally limited to gaseous or liquid samples. It has been discovered that there is a need for a system which will allow chromatographic analysis of filters which have trapped solids or other materials such as volatiles thereon. There is a need in the area of environmental protection testing of exhaust gases such as with combustion engine emission testing. Specifically tests which use particulate filters to collect carbon soot, lubrication oil volatiles, fuel volatiles, and other components of the exhaust gases. Previous methods for exhaust emissions testing, such as indirect testing of collected exhaust constituents, have been complicated, expensive and time consuming. Prior to the present invention, chromatography devices were not well suited for direct analysis of filter collected particulate matter and volatiles.
In other fields there have been injection systems and methods for thermal analysis of geological samples to obtain information useful in petroleum exploration. One example is disclosed in U.S. Pat. No. 4,357,836 issued to Kokesh Nov. 9, 1982. In this method a solid sample such as small granules or powdered of geological specimens are placed in a quartz tube the ends of which are enclosed by gas permeable quartz felt. The quartz tube is wrapped with a wire heater coil which holds the quartz tube in which the sample is contained. The heating coils and sample are inserted into an injection port a portion of which is cooled with a complex fluid circulation system. Fluid such as air is cooled and then blown through baffles arranged in an annular space surrounding the port. A carrier gas is introduced into the port through a gas inlet while the sample is in the cooled zone. Gas blows through the port and exists through the gas chromatograph column for about 1 to 2 minutes until stabilization is reached. Subsequently, the heater coil probe holding the glass or quart tube with the sample therein is moved to a portion of the port for heating. The temperature of the geological sample material is then raised either to accomplish thermal extraction in the range 100.degree. C. to about 400.degree. C., to accomplish pyrolysis at temperatures of about 350.degree. to about 1000.degree. C. The gaseous materials generated from the sample mix with the carrier gas and flow into the gas chromatography column. This apparatus and method is not well suited for direct filter analysis and is complex and cumbersome. It would require placement of the solid matter in granule form into a gas permeable quartz tube. The quartz tube must be carefully placed for holding in a heating coil probe. The system requires the use of special cooling circulation and apparatuses associate with that system. Moreover, there is a substantial waste of energy as the entire port is constructed of heat conductive material so that the cool zone and hot zone constantly work against each other. The cooling circulation system expends energy to remove the same heat energy which is expended in the hot zone for thermal extraction or pyrolysis.
Other complex probe sampling apparatuses and sample inlet instruments have also been previously disclosed. For example, U.S. Pat. No. 3,463,012 issued to McKinney, et al Aug. 26, 1969 and also U.S. Pat. No. 4,344,917 issued to Schorno Aug. 17, 1982 disclose devices which have many of the same drawbacks as discussed above. Both of those devices are constructed with a hot zone and a cool zone which are interconnected with thermally conductive material. The heat generated in the hot zone for thermal extraction must be either continuously or periodically removed using a cooling fluid circulation system. Solid samples are placed in quartz tubes having gas permeable quartz wool ends. The McKinney disclosure relies upon the escape of carrier gas through the inlet opening for stabilizing the system and Schorno relies upon the escape of carrier gas through the gas chromatograph column itself. None of these systems, methods or apparatuses is well suited for direct filter analysis.
Traditional methods of simulated distillation analysis to determine the components in the exhaust use a single time or temperature on the response cure to estimate the boiling point of the fuel (typically 369.degree.). Any constituants shown in the gas chromatograph response below this temperature are considered to be unburned fuel and any constituants above are considered to be the lubricating oil. This can result in an inaccurate reading as some fuel components evaporate at higher temperatures and some oil constituants evaporate at lower temperatures.